"I dont like criticism of my family," James Carter IV tells NBC News.

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Republican presidential candidate and former Massachusetts Gov. Mitt Romney speaks to reporters about the secretly taped video from one of his campaign fundraising events.

Updated at 8:36 AM EDT on Wednesday, Sep 19, 2012

The grandson of former president Jimmy Carter revealed he helped expose the secret Romney fundraiser video that sparked a firestorm on the campaign trail. He said his motivation “is to help get Democrats elected” and to get back at the GOP presidential nominee for his criticism of his grandfather's presidency.

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He told NBC News that he e-mailed his grandfather Mother Jones’ story about the tape and was congratulated Tuesday morning. "James: This is extraordinary. Congratulations! Papa," Carter said the former president responded.

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The leaked video appeared on the website of the liberal magazine Mother Jones Monday and showed Romney speaking to supporters about Obama voters who he did not expect to vote for him.

“There are 47 percent of the people who will vote for the president no matter what," Romney said on the recording. "All right, there are 47 percent who are with him, who are dependent upon government, who believe that they are victims, who believe the government has a responsibility to care for them, who believe that they are entitled to health care, to food, to housing, to you name it.”

The source who shot the video told NBC News that it documented a May 17, $50,000-a-plate fundraiser at the home of private equity titan Marc Leder in Boca Raton, Fla.

After Democrats seized on the comments, Romney conceded late Monday that they were "not elegantly stated" and "off-the-cuff." Romney did not apologize, though, and instead reiterated his belief that Obama's campaign relied upon voter dependency.

James Carter IV told NBC News that he tracked down via Twitter the source who taped Romney speaking to supporters at the closed-door fundraiser.

After coming across a video on YouTube, he eventually connected with its source on Twitter and persuaded the source to release the full tape to Mother Jones magazine, Carter said.

Carter, 35, described himself as a “partisan Democrat” and said he is currently unemployed and did not get paid by the Obama campaign or a political organization for his role in exposing the tape, NBC News reported.

In accepting the GOP nomination for president earlier this month, Romney said in his prepared remarks that “every president since the Great Depression who came before the American people asking for a second term could look back at the last four years and say with satisfaction: ‘you are better off today than you were four years ago.’ Except Jimmy Carter. And except this president.”

Days earlier, Ryan said that, "simply put, the Jimmy Carter years look like the good old days compared to where we are right now.”

Peter Wehrer, a former deputy director of speechwriting for President George W. Bush and who also worked in the George H.W. Bush and Ronald Reagan administrations, told Politico in May that invoking Carter “lightens up certain regions of the mind and brings to mind ineptness and incompetence.”

In alerting his grandfather to the Mother Jones video story, James Carter IV used the subject line “huge campaign news,” and wrote that it was “my biggest story yet.”

He detailed how he said he persuaded the source that shot the video to release it to the press.

In late August, shortly before the Republican National Convention, Carter said he came across a brief YouTube clip where Romney was talking about his investment in a Chinese company.

The link was originally posted under the name “Rachel Maddow” then reappeared under the account "Anne Onymous" because the poster did not have a connection to the MSNBC host.

Carter said the video “piqued my curiosity,” and after tweeting a link to the video noticed that a Twitter user under the name "Anne Onymous" had begun following him on the service.

He then initiated a conversation that convinced the follower to hand over the video to Mother Jones, Carter told NBC News.